1. Field of the Invention
This invention relates to a pneumatically driven power tool, more particularly to a pneumatically driven power tool with a mounting housing in which front and rear bearing assemblies are insertably mounted so as to form a compact size.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional pneumatic tool 1 is shown to include a front housing 111, a rear housing 10, and a middle housing 11 with a mounting housing 112 and a handle 117. The handle 117 defines air inlet and outlet passageways 115,116 which extend in a longitudinal direction. The mounting housing 112 is connected to the front and rear housings 111,10 at front and rear ends thereof by a plurality of screw bolts 110 so as to form a receiving chamber 114 in a transverse direction relative to the longitudinal direction. A work output device 12, a front bearing seat 13, a motor cylinder 14 and a rear bearing seat 16 are disposed in the receiving chamber 114. The rear housing 10 has a receiving concavity 101 for receiving the rear bearing seat 16. An air regulator 17 is disposed in the inlet passageway 115. A regulator shaft 18 is disposed on the rear housing 10.
The motor cylinder 14 has an eccentric chamber 141 formed therein for receiving a driven shaft 15. The driven shaft 15 is mounted on the front and. rear bearing seats 13,16 at two ends thereof. The rear housing 10 is formed with forward and reverse guiding slots 102,103 around the receiving concavity 101, and a mounting hole 104 which extends in the transverse direction to communicate with the forward and reverse guiding slots 102,103. Forward and reverse outlet holes 106,107 and an inlet hole 105 are formed to communicate with the mounting hole 104 so as to communicate with the outlet passageway 116 and the inlet passageway 115. The forward and reverse outlet holes 106,107 are communicated with the forward and reverse guiding slots 102,103. The regulator shaft 18 has annular forward and reverse grooves 181,182. The rear bearing seat 16 has forward and reverse through holes 161,162.
When the forward groove 181 of the regulator shaft 18 is communicated with the inlet hole 105 and the forward guiding slot 102, compressed air can introduced into the eccentric chamber 141 via the inlet passageway 115, the inlet hole 105, the forward groove 181, the forward guiding slot 102, and the forward through hole 161 so as to actuate a forward operation of the driven shaft 15 for the work output device 12. Then, most of the compressed air introduced into the eccentric chamber 141 will be discharged from the outlet passageway 116 via outlet ports 142 disposed on the cylinder 14. A small portion of the compressed air will be discharged via the reverse through hole 162, the reverse guiding slot 103, the reverse groove 182, and the reverse outlet hole 107 A reverse operation of the driven shaft 15 is achieved in the same manner when the reverse groove 182 of the regulator shaft 18 is communicated with the inlet hole 105 and the forward guiding slot 102.
Since the conventional pneumatic tool has the front, rear and middle housings 111,10,11 which are connected together by a large number of the screw bolts 110 in a precise manner, the task of assembly as such is relatively inconvenient to conduct, and results in a bulky tool.